1. Field of the Invention
This invention relates to improvements in so called "voltage blocks", devices for the isolation of components of a system which are maintained at high magnitude positive or negative electrical potential from typically grounded system components even in the presence of continuous or intermittent flow of, for example, an electrically non-insulative fluid therebetween. Thus, throughout this application, the term voltage block is used to describe devices which function to minimize, to the extent they can, the flow of current. Such current would otherwise flow from first system components maintained at high magnitude electrical potential through a stream of electrically non-insulative fluid, such as water-base coating material, flowing between the first components and second system components maintained at high magnitude electrical potential of opposite sign, or much lower magnitude electrical potential, for example, ground potential.
As used herein, the term "electrically non-conductive" means electrically more insulative than the term "electrically conductive." The term "electrically non-insulative" means electrically more conductive than the term "electrically insulative." As used herein, the term "solvent" means any material or material mixture that will dissolve, suspend, emulsify or otherwise act to remove and carry away coating material residue from components of the system described herein. The solvent functions to remove the paint film from inside surfaces of the valve and carry away the paint residue. The disclosed solvents are electrically highly insulative to prevent current conduction between coating material ports on the valve of the invention. The coating material ports are also spaced apart a sufficient distance that the dielectric strength of the solvent between the coating material ports on the valve prevents arcing between the coating material ports. Illustratively, the distance separating the ports is larger than about one inch (about 2.5 cm), and in an illustrative embodiment the movable component of the valve has a diameter of about 2.36 inches (about 6 cm). The solvent thus should meet the criteria of being electrically non-conductive, having minimal ability to suspend coating material solids, and have adequate coating material stripping or cleaning power.
The invention is disclosed in the context of several systems for atomizing and dispensing electrostatically charged particles of coating materials that are bulk electrical non-insulators such as water-based coating materials. However, it is believed to be useful in other contexts as well.
2. Description of the Prior Art
Many voltage blocks are illustrated and described in the prior art. There are, for example, the voltage blocks illustrated and described in U.S. Pat. Nos. 4,878,622; 4,982,903; 5,033,942; 5,154,357; and 5,193,750, and the references cited in those patents, particularly including U.S. Pat. Nos. 1,655,262; 2,547,440; 2,673,232; 3,098,890; 3,122,320; 3,291,889; 3,893,620; 3,933,285; 3,934,055; 4,017,029; 4,020,866; 4,085,892; 4,275,834; 4,313,475; 4,383,644; and, 4,413,788, and U.K. Patent Specifications 1,393,333 and 1,478,853. Also of interest are U.S. Pat. Nos. 2,814,551; 3,838,946; 4,030,860; 4,232,055; 4,381,180; 4,386,888; 4,515,516; 4,741,673; 4,792,092; 4,879,137; 4,881,688; 4,884,745; 4,932,589; 4,962,724; 5,078,168; 5,096,126; 5,102,045; 5,102,046; 5,197,676; 5,249,748; and, 5,255,856. No representation is intended by this listing that this is a complete listing of all pertinent prior art, or that a thorough search of all pertinent prior art has been conducted, or that no better prior art exists. Nor should any such representation be inferred.